In-situ remediation and vitrification of contaminated soils, deposits and buried materials

ABSTRACT

A method is disclosed in which a plasma arc torch is used to vitrify and remediate a site containing contaminated soils, resulting from a hazardous material deposit or spill, or contaminated buried objects. The contaminated earthen material or subterranean deposit is pyrolyzed, melted or solidified by the plasma torch which is energized at the bottom of a cased, vertical borehole, and then gradually raised to the surface. An array of boreholes, appropriately spaced, will remediate an entire mass of contaminated material. Similarly, burled objects such as metal drums containing contaminants and underground storage tanks may be selectively remediated at their specific buried depth. Similar use is made of the plasma torch in a second embodiment with the additional step of processing at selected underground locations in the borehole array to create a sealed horizontal layer, vertical cutoff walls or a sealed basin as a barrier against further leaching of contaminants into surrounding soil and groundwater. Gaseous by-products of the pyrolysis process are collected, treated and processed, as appropriate.

FIELD OF INVENTION

The invention disclosed relates to the field of remediation andvitrification of soils containing hazardous materials at or beneath thesurface of the earth.

REFERENCE TO RELATED APPLICATION

Two related copending applications provide useful background for thepresent application. One is U.S. patent application Ser. No. 07/827,384filed Jan. 29, 1992 for "IN-SITU SOIL STABILIZATION METHOD ANDAPPARATUS", and the second is the application entitled "IN-SITU LANDFILLPYROLYSIS, REMEDIATION AND VITRIFICATION" filed Aug. 17, 1992.

BACKGROUND OF THE INVENTION

A serious contemporary problem is the accidental spilling or intentionaldiscarding of toxic or environmentally hazardous materials comprisingboth organic and inorganic contaminants. These injurious materials maybe liquid or solid, and may be at the ground surface or buried. Whensuch a situation occurs, the land affected can be permanently destroyedfor productive use, or at least until an expensive clean-up process isaccomplished. In addition to the effect on the soil, such contaminatingwastes often find their way into streams, rivers and municipal watersupplies, causing untold damage and potential sickness. Such hazardouswaste materials include, by way of example, petroleum products,chemicals, mine tailings, sludges, and low-level radioactive materialswhether exposed or contained in metal drums or underground storagetanks.

The sort of clean up operations which have been done in the past haveinvolved excavating the contaminated soils or objects, and transportingthem to a treatment facility or to a safe storage site. Alternatively,means of remediating contaminated soil in-situ have been outlined inU.S. Pat. No. 4,376,598 to Brouns et al., for "In Situ Vitrification ofSoil". The '598 patent teaches the insertion of two or more conductivegraphite electrodes into the soil, providing a conductive electricalpath on the surface of the soil, and generating a current through theelectrical path to heat the surrounding soil to its melting temperature.Once a melted soil stream has been established between electrodes, themolten soil provides the conductive path. However, this method hasseveral drawbacks; e.g., soil melting must begin at the ground surfaceand proceed downward, it cannot operate at deep depths or at selectivedepths, the continuity of the soil electrical path is not reliable, andrestarting the current flow once the melt has moved below ground surfacelevel is quite difficult. In addition, since processing temperatures arebelow 2000° C., soil additives may be necessary to lower the meltingpoint of particular soils, and the method does not work well if there istoo much metal or moisture in the soil.

The invention disclosed herein recognizes that there exists a relativelynew technology which may be employed in the remediation of allcontaminated soils or buried materials at any depth by the process ofpyrolysis, melting and vitrification of waste materials using largequantities of very high temperature heat energy. The basic tool used inthis technology is the plasma arc torch. Plasma arc torches canroutinely operate at energy levels ranging from 100 kw to 10 MW. Plasmatorches produce temperatures of 4000° C. to 7000° C. in the range of85-93% electric to heat energy conversion efficiency. For purposes ofcomparison, the highest temperature attainable by fuel combustionsources or the aforementioned graphite electrode process is in thevicinity of 2700° C.

A plasma arc torch operates by causing a high energy electric arc toform a stream of plasma, or ionized gas, thus generating large amountsof heat energy. There are many types of plasma torches. ., but alltorches.!.. .Iadd.A plasma torch can operate on AC or DC power, usinginert, reducing or oxidizing gas, and have metal or graphite electrodeswhich may be solid or hollow. All plasma torches .Iaddend.generally fallinto one of two basic categories according to the arc configurationrelative to the torch electrodes, i.e., transferred arc type andnon-transferred arc type. The arc of a transferred arc torch is formedby and jumps from a single electrode on the torch, through the plasmagas, and to an external electrode which is connected to the oppositeelectrical terminal. The arc of a non-transferred arc torch is formed byand jumps from one electrode on the torch along the plasma gas and backto another electrode on the torch.

In the plasma arc torch, the heat energy produced is proportional to thelength of the arc, assuming the type of plasma gas and appliedelectrical current both remain constant.

Since the present invention makes use of a plasma arc torch, referenceis next made to U.S. Pat. No. 4,067,390 granted to the present inventorsfor "Apparatus And Method For The Recovery Of Fuel Products FromSubterranean Deposits Of Carbonaceous Matter Using A Plasma Arc" whichpatent teaches the use or a plasma arc torch to gasify or to liquifyunderground deposits of coal, oil, oil shale, tar sands and othercarbonaceous materials. The teachings of the '390 patent areincorporated hereby by reference.

It is a major objective of the invention to afford an efficient andenvironmentally safe system for the in-situ remediation of soilscontaining hazardous materials and other buried contaminants such asmetal drums or waste matter, underground storage tanks and other toxicdeposits.

It is a further objective of the invention to prevent the leaching andspread of contaminated material to the surrounding soil medium and tothe subterranean water system.

Additional objectives of the invention will become apparent from thedisclosure which follows.

SUMMARY OF THE INVENTION

The invention disclosed utilizes plasma torch heating for theremediation by in-situ pyrolysis and vitrification of hazardous wastesites, spills or deposits buried at any depth below the ground surface.A series of boreholes are formed throughout a contaminated area in anarray such that the perimeters of the vitrified, solidified orremediated columns which are formed will coalesce together. A plasma arctorch is inserted, energized and moved within each borehole so as toform a column of material which has been remediated by pyrolysis of theorganic material in the soil and vitrification of the surroundingcontaminated inorganic soils and buried materials. The gases generatedin this process are collected at the top of each borehole and treated asrequired. Upon cooling, the molten mass solidifies into a dense, inert,vitrified mass which effectively immobilizes and neutralizes anyremaining contaminants. Certain contaminants may be remediated withinsolidified or devolatilized zones which extend beyond the vitrifiedzone. In these situations, the borehole spacing would be increased.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional elevation view of a typical hazardous spill siteshowing the contaminated areas of soil radiating from the initial spilllocation into the surrounding soil.

FIG. 2 is the view of FIG. 1 with an initial borehole formed into theearth, with a plasma torch inserted in the borehole and with a gascollector positioned above the borehole according to the invention.

FIG. 3 is a top plan view of an area of a hazardous material spillshowing a typical pattern of boreholes drilled at an extended spacingand the resultant coalesced columns of melted, solidified anddevolatilized soil treated to immobilize and remediate thecontamination.

FIG. 4A is a sectional elevation view of an underground site containingburied drums of hazardous materials, with contaminated materialradiating into the surrounding soil.

FIG. 4B is a sectional elevation view of an underground site having asubterranean liquid storage tank, with contaminated material radiatingfrom a leak in the storage tank.

FIG. 5 is a perspective illustration of leachate cutoff walls and acontainment basin established according to the present invention.

FIG. 6 is a sectional elevation view of a site of a hazardous liquidsurface spill having leached into surrounding soil to a small extent anda plasma torch suspended above the spill site.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The invention relates to the problem illustrated, by way of example, inFIG. 1, showing a spill of liquid material, hazardous waste 50, onto theupper surface of a section of earth. Over a period of time, thehazardous waste 50 leaches along the surface and into the ground 52,thereby creating contaminated area 54 which extends for some distance inall directions from the original site of the spill. Uncontaminated earth52 beyond the contaminated area 54 is unaffected, although in sufficienttime the leaching will typically continue until the contaminated area 54encompasses a much larger area red could ultimately reach an undergroundaquifer which would permit the hazardous waste 50 to migrate along itspath of flow. In other situations, the hazardous spill or deposit may bea solid substance or a buried object, but its contaminating effect isalso subject to leaching and migration into the surrounding earth andwater with the aid of rain.

As shown in FIG. 2, a borehole 57 is formed by drilling through thecontaminated soil mass 54 to a point just below the maximum depth ofcontamination and a thin heat-destructible metal casing (not shown) isinserted into the hole. The metal casing serves to prevent collapse ofthe sidewalls of borehole 57, facilitate the up and down movement ofplasma arc torch 56 within the borehole 57, and to permit gases formedby the pyrolysis process to quickly reach the surface for collection andtreatment. Next, plasma torch 56 is lowered to a point near the bottomof borehole 57 and is suspended by supply conduit 58 which containselectrical cables, a plasma gas supply line and coolant water necessaryfor torch operation as described above. The process of lowering andraising plasma torch 56 is accomplished by means of appropriate liftequipment (not shown).

The torch 56 is also provided with a protective heat shroud 60 adaptedto shield the supply conduit 58 from being damaged by the heatgenerated. In the treatment of shallow contaminated deposits, thisshroud would extend to the ground surface. When energized in thenon-transferred mode, as is preferred, plasma arc 62 is established atthe lowest point in borehole 57 and slowly raised to the top of the holeto gasify, pyrolyze, and melt a column of the surrounding earth andcontaminants. Since the plasma torch is capable of creating temperaturesin the range of 4000° C. to 7000° C., the heat produced gasifies andpyrolyzes all organic materials in the presence of steam in the soilimmediately surrounding the borehole. It is preferred according to thesubterranean embodiment disclosed to operate plasma torch 56 in thenon-transferred arc mode.

The gases are collected at the top of the borehole 57 for treatment, asrequired, by standard gas treatment technology. A gas collection hood 61is positioned over borehole 57 to channel the generated gas to alocation for treatment. The inorganic materials and the soil are meltedand, when allowed to cool, become a virtually unleachable and relativelynonporous, dense vitrified mass. This process of gasification,pyrolysis, melting and cooling, according to the invention, is done withan array of individual boreholes creating a group of treated columnswhich will coalesce together over the entire site (see FIG. 3) whichcontains the hazardous material.

As depicted in FIG. 2, the heat energy from plasma torch 56 radiates ina generally spherical pattern with the greatest degree of heat closestto plasma arc 62, and with the temperature lessening with greaterdistance from the plasma arc 62. Therefore, the area closest arc 62 iscompletely vitrified and the more distant portions of earth 66, 68 areheated to a lesser degree as will be described below.

Immediately beneath plasma arc 62, molten waste 64 generated attemperatures above 1100° C. accumulates in a pool. Beyond the distanceto which sufficient heat for soil melting and vitrification hastravelled, the curing zone 66 is subjected to sufficient heat (typically900° C. or greater) to cure the earthen material into a brick-likehardness. The third zone in terms of distance from plasma arc 62 is adeplasticized zone 68 which is not cured, but has all liquid permanentlyremoved therefrom by exposure of 200° C. or more and effectively becomesa rigid, non-absorbent envelope of soil. The distance to which heat willtravel and effectively generate cured zone 66 and deplasticized zone 68depends upon the power levels generated by plasma torch 56, the moisturecontent of the soil, and the nature of the surrounding contaminatedearth 54 and uncontaminated earth 52.

The spacing between adjacent boreholes 57 is based in part on the natureof the contaminating materials and in part on the degree of soilvitrification and solidification required to contain, immobilize, andneutralize those materials.

As plasma arc torch 56 continues to generate heat energy, to meltportion 64 and to cure and deplasticize portions 66 and 68 respectively,torch 56 is gradually raised by appropriate mechanisms (not shown). Thelifting mechanism for torch 56 is optionally either manually orautomatically controlled. Movement of plasma arc torch 56 upwardly inborehole 57 melts and solidifies increasingly higher sections ofcontaminated earth 54 into a column until torch 56 reaches the topsurface of the earth. The molten material 64 occupies substantially lessvolume than the soil from which it is formed due to the gasification oforganic material, elimination of the water in the soil and thedensification caused by the vitrification process. This will result in asignificant subsidence in the original ground surface surrounding theborehole 57 as shown in FIG. 2. Therefore, the result of the process is,after removal of the torch 56 and cooling of the molten material, asignificantly reduced volume of hard, dense rock-like material in asubsided column encompassing the former borehole location.

The basic nature of a plasma arc torch is that of generating heat byelectric arc as opposed to any sort of combustion. The process employed,therefore, does not require air or oxygen. The amount of plasma gasrequired to sustain an arc is on the order of 10 times less than theamount of air which is required to combust a fuel and generate similaramount of heat energy. Because of this lack of oxygen, even if air wereto be the chosen plasma gas, no combustion of organic contaminants, suchas petroleum spill products, is possible.

To completely treat the area affected by the leaching into soil 54 ofcontaminant 50, an array of holes encompassing the area must be formed.A typical array is that shown in FIG. 3 which generally depicts a topplan view of the contaminated soil situation of FIGS. 1 and 2 afterhaving been drilled and processed with plasma arc torch 56 as discussedabove. In the approximate center of FIG. 3 is an illustrative surfacehazardous waste spill 50 with contaminated area 54 indicated within adashed line. The spacing of the boreholes 57 in the array of FIG. 3 isdependent upon the nature of the soil and the type of contaminant whichis present. According to the method of the invention, an initialborehole 57 is drilled and processed with a plasma arc torch 56 so as todetermine the actual maximum diameter which can be effectivelydecontaminated and remediated. The placement of successive boreholes 57is such that sufficient overlapping of treated material occurs toremediate the entire affected area. In a typical drilling and heattreatment site with increased borehole spacing, cooled vitrified soilmass 70 is shown surrounded by cured brick-like zone 72 anddeplasticized zone 74. The final result of the processed array ofboreholes 57 is that at least all areas represented by deplasticizedzone 74 are coalesced together so that all contaminated earthen material54 is either gasifier, pyrolyzed, vitrified or otherwise immobilized.This resultant remediated soil is no longer harmful and will protectagainst further spread of the hazardous spill.

A relatively large spacing of boreholes 57 to coalesce the deplasticizedzones as described above would be appropriate to treat and remediatesoil contamination of simple organic volatile compounds such aspetroleum products. The pyrolysis process would rapidly volatilize thiscontaminant out to the edge of the deplasticized zone 68 of FIG. 2(temperatures greater than 200° C.). Medium borehole 57 spacing tocoalesce the brick-like zone 66 of treated material (temperaturesgreater than 900° C.) should be considered for such contaminants asorganic solids, sludges, or non-organic compounds of low toxicity.Finally, close spacing of boreholes 57 will be required to coalesce thethermally treated columns of the vitrified zone 64, which has beenmelted by heating to temperatures exceeding 1100° C. The contaminantsrequired to be fully melted, vitrified and immobilized would includehighly hazardous/toxic inorganic materials, such as heavy metals,low-level radioactive wastes, and underground deposits of unknowncontaminants such as that found in unrecorded, buried metal drums 76 ofwaste (FIG. 4A). Over time, such buried drums are prone to rusting andleakage, causing an area of contaminated soil 54, as is illustrated.

A specific borehole spacing for a particular site remediation programwould be ultimately determined by analysis of the results of an in-situvitrification test in the medium to be remediated.

The invention also includes subterranean remediation capabilities uniqueto plasma arc torch processing of contaminated materials. Principalamong these unique capabilities are the ability to operate at any depthunderground, selective depth remediation of buried contaminants, and theremediation of contaminants located below the groundwater table. Anexample of selective remediation is the insertion of the plasma torch 56directly into an underground storage tank 78 (FIG. 4B) which wouldreadily remediate and volatilize all the residual petroleum products inthe tank. If necessary, the plasma torch could be operated until thestorage tank itself is melted and any surrounding contaminated soil 54,as would seep from break 55, is vitrified or otherwise remediated. Theaccompanying ground surface subsidence into the cavity of the storagetank would be backfilled with clean material.

If the contaminant situation is one in which leaching has progressed nomore than a small distance beneath the surface, e.g. 50 cm or less, itis not typically necessary to drill a hole. Thorough pyrolysis andvitrification can be accomplished with the plasma arc torch suspended aselected distance H above the ground surface, e.g., approximately 30centimeters for a 1 MW plasma torch and radiating heat downwardly (seeFIG. 6). In this surface application, the transferred arc torch modewould be the preferred remediation configuration. In the transferred arcmode, a second electrode (not shown) is driven into the ground in thevicinity of the spill to complete the electric circuit. This process isrepeated at appropriately spaced locations until the entire spill isremediated. Whether operating above or below ground level, it ispractical in many situations to utilize several torches simultaneouslyand reduce the total time required to remediate the hazardous deposit.

In certain situations, when a spilled or buried contaminant covers avery large area, is leaching rapidly or imminently threatening a watersupply, it may be desirable to employ a second embodiment of theinvention as described below. Correction of such a condition requiresthe first priority to be the creation of a barrier against furtherspreading of the seeping, contaminating leachate.

The initial steps of forming a borehole 57 to a depth shown in FIG. 2,inserting a thin metal casing (not shown), inserting and energizing aplasma arc torch 56 remain as described above. However, in order totreat an area as quickly as possible according to the second embodiment,plasma torch 56 is deenergized after pyrolyzing, melting and solidifyingsections 64, 66 and 68 surrounding flame 62; torch 56 is then removedfrom borehole 57 without gradually being lifted and melting verticallyup to the ground surface. Torch 56 is subsequently lowered into each ofthe other boreholes 57 illustrated in the array of FIG. 3 to beenergized at or near the same depth so as to create a coalescedhorizontal sealant layer 82 (FIG. 5) below the depth of the leachingcontaminant which layer acts as a non-porous sealant to protect againstfurther vertical leaching. After creation of this sealant layer 82through treatment of the deepest portions of all holes 57, it may bedesirable to reintroduce the plasma torch into each of the peripheralboreholes 57 so as to continue to pyrolyze, melt, and vitrify the soilfrom the level of the established horizontal sealant layer 82 up to theground surface, thereby establishing one or more substantially verticalsealant cutoff walls of coalesced columns 80 from the horizontalcontainment layer up to the ground surface. The result is essentially avitrified, impermeable set of cutoff walls or a complete sealed basin toprevent further leaching into surrounding soil 52. Following thecreation of this barrier, the plasma torch could be reintroduced intothe existing boreholes as a lower priority to remediate the entirevolume of contaminated material.

As mentioned earlier, even if contaminants have reached the ground watertable and are migrating out of the original contaminated area, plasmatorch remediation still presents a viable solution. Plasma torches havebeen shown to work well underwater and at selective locations anddepths. Therefore, once located, the contaminants migrating within theaquifer or underground stream could be readily pyrolyzed and vitrifiedalong with the surrounding media and immobilized from further migration.In the case of any leached contaminant, it is essential to quicklydetermine the extent of spread of the contamination and to positionboreholes 57 accordingly.

The plasma torch soil remediation process of the invention, because ofthe very high temperature created, will act to volatilize and pyrolyzethe organic contaminants and generate gaseous by-products. The off-gasesare collected by means of a hood 61 (FIG. 2) and scrubbed or chemicallycleaned, as is known. Any residual carbon in the soil, together with theinorganic contaminants, would be melted into a slag which, when cooled,results in a high density, inert vitrified mass, which is not subject toleaching.

In summary, the process of the invention disclosed herein provides ahighly reliable, efficient and environmentally safe method ofremediating problems of soil contamination by intentional or accidentalwaste spills and deposits on or below the surface of the earth. Theplasma arc torch method will pyrolyze, melt and vitrify any contaminatedsoil or rock material deposit or object and produce gaseous by-productsaccording to the material being processed. Organic and inorganicmaterials, including heavy metals, can be processed and remediated atany depth or location underground, leaving an environmentally safe andchemically inert residue containing immobilized residual contaminants.Testing of the invention process in accordance with standards of theUnited States Environmental Protection Agency has demonstrated hazardouschemical levels in the inert residue lower than one-tenth thepermissible concentration for leachability.

It is understood that the specific embodiments are used herein asexamples and are not to be construed as limitations on the scope andprinciples of the invention.

What is claimed is:
 1. A method for in-situ remediation andvitrification of hazardous waste contaminated soil comprising .Iadd.thesteps of.Iaddend.:(a) forming a vertical borehole of a size sufficientto accommodate a plasma arc torch.Iadd., said vertical borehole.Iaddend.extending from an upper surface of the soil to a lower end at apredetermined depth in said hazardous waste contaminated soil; .Iadd.(b)inserting a casing into said formed borehole for preventing sidewallcollapse; .Iaddend. (. .b.!..Iadd.c.Iaddend.) lowering a plasma arctorch together with connected utilities into said . .formed borehole.!..Iadd.casing .Iaddend.and suspending the plasma arc torch at a locationabove and proximate said borehole lower end; (. .c.!..Iadd.d.Iaddend.)utilizing the connected . .plasma torch.!. utilities to operate saidtorch .Iadd.to convert electrical energy to heat so as .Iaddend.tocreate a plasma arc of sufficient temperature to pyrolyze and melt ..substantially in the absence of combustion.!. a portion of saidcontaminated soil located proximate said plasma arc; (..D.!..Iadd.e.Iaddend.) deenergizing the plasma arc torch; (..e.!..Iadd.f.Iaddend.) removing the plasma arc torch from the borehole;and (. .f.!..Iadd.g.Iaddend.) allowing said molten soil to cool andsolidify thereby to produce a vitrified column of hard, inert residuesubstantially less in volume than the contaminated soil from which itwas produced.
 2. The method for in-situ remediation and vitrification ofhazardous waste contaminated soil as claimed in claim 1 in which saidborehole is formed to a depth greater than the depth of saidcontaminated soil.
 3. The method for in-situ remediation andvitrification of hazardous waste contaminated soil as claimed in claim
 1. .including the step of inserting a heat destructible casing into saidformed borehole prior to lowering said torch therein.!. .Iadd.furtherincluding the step of forming said casing of a heat destructiblematerial.Iaddend..
 4. The method for in-situ remediation andvitrification of hazardous waste contaminated soil as claimed in claim 3further comprising gradually raising said torch in said borehole so asto melt sequentially higher portions of contaminated soil.
 5. The methodfor in-situ remediation and vitrification of hazardous wastecontaminated soil as claimed in claim 3 in which said plasma arc torchoperates to melt a portion of contaminated soil only at the lowest depthto which the borehole is formed and is then removed from said borehole,and such process is repeated in each of the plurality of boreholes so asto form a coalesced and non-porous horizontal sealant layer to preventfurther vertical leaching of contaminants to surrounding soil andaquifers.
 6. The method for in-situ remediation and vitrification ofhazardous waste contaminated soil as claimed in claim 1 wherein saidborehole is formed as an initial hole and further comprising lowering,operating, and raising said torch so as to determine from said initialhole the effective diameter of said decontaminated and vitrified soiland thereby to determine the distance required between said initial holeand a remaining plurality of holes in order to completely vitrify andremediate an area containing said hazardous waste contaminated soil. 7.The method for in-situ remediation and vitrification of hazardous wastecontaminated soil as claimed in claim 6 further comprising forming aplurality of boreholes each at a distance from adjacent boreholes sothat the peripheral diameters of solidified materials as determined fromthe initial hole will coalesce and form a solidified mass throughout thearea containing said hazardous waste contaminated soil.
 8. The methodfor in-situ remediation and vitrification of hazardous wastecontaminated soil as claimed in claim 7 further including the step ofpositioning said plurality of boreholes in such relative proximity sothat the heat transmitted from said plasma torch through saidcontaminated soil beyond the portion being melted creates peripheralzones of solidified brick-like material and deplasticized material andthe outer deplasticized material of each hole is coalesced with therespective deplasticized material formed around adjacent boreholes. 9.The method for in-situ remediation and vitrification of hazardous wastecontaminated soil as claimed in claim 1 including the step of operatingsaid plasma torch in a non-transferred mode. . .10. A method for in situremediation and vitrification of hazardous waste contaminated soilwherein the contamination extends to only a shallow depth below thesurface of the soil, comprising:(a) suspending a plasma arc torchtogether with connected utilities above said contaminated soil; (b)utilizing the connected plasma torch utilities to operate said torch tocreate a plasma arc of sufficient temperature to melt substantially inthe absence of combustion a portion of said contaminated soil locatedproximate said plasma arc; (c) deenergizing the plasma arc torch; and(d) allowing said molten mass to cool and solidify thereby to produce avolume of vitrified soil substantially less in volume than thecontaminated soil from which it was produced..!.. .11. The method forin-situ remediation and vitrification of hazardous waste contaminatedsoil as claimed in claim 10, further comprising moving said plasma arctorch to additional adjacent locations above said contaminated soil andremediating and vitrifying said additional adjacent locations ofcontaminated soil..!.. .12. The method for in-situ remediation andvitrification of hazardous waste contaminated soil as claimed in claim11 further comprising operating said torch in a transferred arcmode..!.13. The method for in-situ remediation and vitrification ofhazardous waste contaminated soil as claimed in claim 1 wherein saidborehole is formed to a depth substantially equal to the depth of saidhazardous waste contaminated soil.
 14. The method for in-situremediation and vitrification of hazardous waste contaminated soil asclaimed in claim 1 wherein said hazardous waste contaminated soil ..comprises.!. .Iadd.includes .Iaddend.volatile compounds and.Iadd.further .Iaddend.including .Iadd.the steps of .Iaddend.formingthroughout the contaminated soil area a plurality of boreholes each at adistance from adjacent boreholes and volatizing said volatile compoundsin each of said boreholes.
 15. The method for in-situ remediation andvitrification of hazardous waste contaminated soil as claimed in claim 1further comprising forming a plurality of boreholes each at a distancefrom adjacent boreholes so that the peripheral diameters of solidifiedmaterials as determined from the initial hole will coalesce and form asolidified mass throughout the area containing said hazardous wastecontaminated soil. The method for in-situ remediation and vitrificationof hazardous waste contaminated soil as claimed in claim 1 wherein saidcontaminated soil . .comprises having.!. .Iadd.includes .Iaddend.buriedmetal objects and including during the step of melting said soil the.Iadd.further .Iaddend.step of melting said metal objects in situ. 17.The method for in-situ remediation and vitrification of hazardous wastecontaminated soil as claimed in claim 1 wherein said contaminated soil ..comprises having.!. .Iadd.includes .Iaddend.buried metal objectscontaining volatile products and including during the step of meltingsaid soil the . .step.!. .Iadd.further steps .Iaddend.of melting saidmetal objects in situ and volatilizing . .the.!. said volatile productscontained therein.
 18. The method for in-situ remediation andvitrification of hazardous waste contaminated soil as claimed in claim 1in which said plasma arc torch operates to melt a portion ofcontaminated soil only at the lowest depth to which the borehole isformed and is then removed from said borehole, and such process isrepeated in each of . .the.!. .Iadd.a .Iaddend.plurality of boreholes soas to form a coalesced and non-porous horizontal sealant layer toprevent further vertical leaching of contaminants to surrounding solidand aquifers. .Iadd.19. A method for in-situ remediation andvitrification of hazardous waste contaminated soil comprising the stepsof:(a) forming a vertical borehole of a size sufficient to accommodate aplasma arc torch and extending from an upper surface of the soil to alower end at a predetermined depth in said hazardous waste contaminatedsoil; (b) lowering a plasma arc torch together with connected utilitiesinto said formed borehole and suspending the plasma arc torch at alocation above and proximate said borehole lower end; (c) utilizing theconnected utilities to operate said torch to convert electrical energyto heat so as to create a plasma arc flame of sufficient temperature topyrolyze and melt a portion of said contaminated soil located proximatesaid plasma arc flame; (d) gradually raising said torch in said boreholeso as to melt sequentially higher portions of said contaminated soil;(e) deenergizing the plasma arc torch; (f) removing the plasma arc torchfrom the borehole; and (g) allowing said molten soil to cool andsolidify thereby to produce a vitrified column of hard, inert residuesubstantially less in volume than the contaminated soil from which itwas produced. .Iaddend..Iadd.20. The method for in-situ remediation andvitrification of hazardous waste contaminated soil as claimed in claim19 in which said borehole is formed to a depth equal to or greater thanthe depth of said contaminated soil. .Iaddend..Iadd.21. The method forin-situ remediation and vitrification of hazardous waste contaminatedsoil as claimed in claim 19 including the step of inserting a heatdestructible casing into said formed borehole prior to lowering saidtorch therein. .Iaddend..Iadd.22. The method for in-situ remediation andvitrification of hazardous waste contaminated soil as claimed in claim19 wherein said borehole is formed as an initial hole and furthercomprising the steps of lowering, operating, and raising said torch fordetermining from said initial hole the effective diameter of saiddecontaminated and vitrified soil and thereby determining the distancerequired between said initial hole and a plurality of additional holesin order to completely vitrify and remediate an area containing saidhazardous waste contaminated soil. .Iaddend..Iadd.23. The method forin-situ remediation and vitrification of hazardous waste contaminatedsoil as claimed in claim 19 further comprising the step of forming aplurality of boreholes each at a distance from adjacent boreholes sothat the peripheral diameters of solidified materials as determined fromthe initial hole will coalesce and form a solidified mass throughout thearea containing said hazardous waste contaminated soil..Iaddend..Iadd.24. The method for in-situ remediation and vitrificationof hazardous waste contaminated soil as claimed in claim 19 includingthe step of operating said plasma torch in a non-transferred mode..Iaddend..Iadd.25. The method for in-situ remediation and vitrificationof hazardous waste contaminated soil as claimed in claim 19 in whichsaid plasma arc torch operates to melt a portion of contaminated soilonly at the lowest depth to which the borehole is formed and thendeactivating and removing said plasma arc torch from said borehole, andrepeating such steps in each of a plurality of boreholes so as to form acoalesced and non-porous horizontal sealant layer to prevent furtherdownward leaching of contaminants to surrounding soil and aquifers..Iaddend..Iadd.26. The method for in-situ remediation and vitrificationof hazardous waste contaminated soil as claimed in claim 22 furthercomprising forming a plurality of boreholes each at a distance fromadjacent boreholes so that the peripheral diameters of solidifiedmaterials as determined from the initial hole will coalesce and form asolidified mass throughout the area containing said hazardous wastecontaminated soil. .Iaddend..Iadd.27. The method for in-situ remediationand vitrification of hazardous waste contaminated soil as claimed inclaim 26 further including the step of positioning said plurality ofboreholes in such relative proximity so that the heat transmitted fromsaid plasma torch through said contaminated soil beyond the portionbeing melted creates peripheral zones of solidified brick-like materialand deplasticized material and the deplasticized material of each holeis coalesced with the respective deplasticized material formed aroundadjacent boreholes. .Iaddend..Iadd.28. A method for in-situ remediationand vitrification of hazardous waste contaminated soil comprising thesteps of:(a) forming a vertical borehole of a size sufficient toaccommodate a plasma arc torch and extending from an upper surface ofthe soil to a lower end at a predetermined depth in said hazardous wastecontaminated soil; (b) lowering a plasma arc torch together withconnected utilities into said formed borehole and suspending the plasmaarc torch at a location above and proximate said borehole lower end; (c)utilizing the connected utilities to operate said torch to convertelectrical energy to heat so as to create a plasma arc flame ofsufficient temperature to pyrolyze and melt a portion of saidcontaminated soil located proximate said plasma arc flame; (d)deenergizing the plasma arc torch; (e) removing the plasma arc torchfrom the borehole; (f) allowing said molten soil to cool and solidifythereby to produce a vitrified column of hard, inert residuesubstantially less in volume than the contaminated soil from which itwas produced; and (g) forming a plurality of additional boreholes eachat a distance from adjacent boreholes so that the peripheral diametersof solidified materials as determined from the initial hole willcoalesce and form a solidified mass throughout the area containing saidhazardous waste contaminated soil. .Iaddend..Iadd.29. The method forin-situ remediation and vitrification of hazardous waste contaminatedsoil as claimed in claim 28 in which said plasma arc torch operates tomelt a portion of contaminated soil only at the lowest depth to whichthe borehole is formed and said plasma arc torch is then deactivated andremoved from said borehole, and such process is repeated in each of saidplurality of boreholes so as to form a coalesced and non-poroushorizontal sealant layer to prevent further downward leaching ofcontaminants to surrounding soil and aquifers. .Iaddend.